Barium

Barium,  ₅₆Ba

General properties
Name, symbol	Barium, Ba
Appearance	Silvery-white metal
Barium in the periodic table
Sr ↑ Ba ↓ Ra Caesium ← Barium → Lanthanum
Atomic number	56
Standard atomic weight (Ar)	137.327(7)
Group, block	(alkaline earth metals); s-block
Period	period 6
Electron configuration	[Xe] 6s2
per shell	2, 8, 18, 18, 8, 2
Physical properties
Silvery-white
Phase	Solid
Melting point	1000 K ​(727 °C, ​​1341 °F)
Boiling point	2118 K ​(1845 °C, ​​3353 °F)
Density near r.t.	3.51 g/cm3
when liquid, at	3.338 g/cm3
Heat of fusion	7.12 kJ/mol
Heat of	142 kJ/mol
Molar heat capacity	28.07 J/(mol·K)
pressure
Atomic properties
Oxidation states	+2, +1 ​(a strongly basic oxide)
Electronegativity	Pauling scale: 0.89
energies	1st: 502.9 kJ/mol 2nd: 965.2 kJ/mol 3rd: 3600 kJ/mol
Atomic radius	empirical: 222 pm
Covalent radius	215±11 pm
Van der Waals radius	268 pm
Miscellanea
Crystal structure	​​body-centered cubic
Speed of sound thin rod	1620 m/s (at 20 °C)
Thermal expansion	20.6 µm/(m·K) (at 25 °C)
Thermal conductivity	18.4 W/(m·K)
Electrical resistivity	332 Ω·m (at 20 °C)
Magnetic ordering	Paramagnetic
Young's modulus	13 GPa
Shear modulus	4.9 GPa
Bulk modulus	9.6 GPa
Mohs hardness	1.25
CAS Registry Number	7440-39-3
History
Discovery	Carl Wilhelm Scheele (1772)
First isolation	Humphry Davy (1808)

Barium is a chemical element with symbol Ba and atomic number 56. It is the heaviest non-radioactive s-block element.

Properties

Chemical

Barium slowly oxidizes in air to form a dark layer of barium oxide and barium nitride. Barium and its compounds burn with a green flame. This property allowed it to be used in green fireworks, though in recent years, boron compounds are beginning to replace barium, as they're less toxic.

Barium is readily attacked by acids, though reaction with sulfuric acid forms a protective insoluble layer of barium sulfate, which protects the metal from further corrosion.

Barium reacts with water to release hydrogen gas. Barium hydroxide precipitates:

Ba + 2 H₂O → Ba(OH)₂ + H₂

The same reaction also happens with alcohols, giving barium alkoxide.

Barium reacts with ammonia to form complexes such as Ba(NH₃)₆.

Physical

Barium is a silvery white metal, that rapidly turns black on exposure with air. Barium melts at 730 °C, intermediate between those of the lighter strontium (780 °C) and heavier radium (700 °C). Its boiling point of 1,900 °C is higher than that of strontium (1,382 °C) and radium (~1737 °C). Barium has a density of 3.62 g/cm³

Availability

Barium metal is sold by various chemical suppliers, either under oil or ampouled. GalliumSource sells 50 g of barium at a price of $92.00.

Isolation

Barium can be isolated through the aluminothermic reduction of barium oxide:

4 BaO + 2 Al → 3 Ba↑ + BaAl₂O₄

Due to the high temperatures released during this reaction, the resulting barium metal turns to vapors, which are condensed under argon. This is not easy to do.

Silicon can also be used as a reducing agent.

Projects

• Make barium peroxide
• Make soluble barium salts
• Green flame
• Ellement collecting

Handling

Safety

Barium readily reacts with water releasing hydrogen gas, which is flammable and its build-up may cause explosions. However, unlike alkali metals, it can be safely handled with bare hand.

Soluble barium salts and other compounds are very toxic to organisms and should be handled with proper protection. Insoluble barium compounds however, are pretty much non-toxic .

Storage

Barium metal must be stored away from moisture, air and other corrosive vapors. It is best stored under mineral oil or ampouled, under argon.

Disposal

Barium metal is best converted to barium sulfate, which is non-toxic.

References

Relevant Sciencemadness threads

• Barium Metal